A method for rotor balancing provides for the measurement of rotor imbalance parameters (amount of out-of-balance mass, radius and angle of its center disposition relative to a rotor axis) by means of determining two unbalance vectors (unbalance is a vector quantity that is equal to the unbalanced mass multiplied by its center radius-vector relative to the axis) that are arranged in two arbitrary planes being perpendicular to a rotor axis. These planes are called as imbalance datum planes or imbalance correction planes (see, for example, M. E. Levit, V. M. Ryzhenkov “Balancing of Parts and Units”, Moscow, Mechanical Engineering, 1986).
There are widely known methods for rotor balancing that are based on imparting rotary motion to a rotor and measuring its oscillation amplitudes and phases in the planes being perpendicular to a rotor axis (e.g. EP No. 0150274, 1985). In accordance with this method, the imbalance datum planes are set up with the help of supports, in which a rotor is installed; in doing so, the rotor oscillation amplitudes and phases are measured by means of measuring dynamic loads generated in the supports. A limitation of this method is that parameters to be measured must be exposed to additional processing to share unbalance data in different imbalance datum planes.
There is known a method for rotor balancing, which is based, as the above one, on imparting rotary motion to a rotor mounted on the supports. A peculiarity of this method is that after measurement of oscillation parameters with the rotor to be at a certain position for the purpose of making the rotor imbalance datum planes shared, the rotor is turned by 180° and the rotor oscillation phase and amplitude are measured again, followed by processing the measured parameters and determining the unbalance rate to be found in each of imbalance datum planes (U.S. Pat. No. 5,359,885, 73/146, 1994). A drawback with this method consists in labor intensity and low efficiency.
A method that is realized with the help of a single distributed support, in which the rotor is set up with its one end face, is more convenient in operation. This method is characterized by the rotor to be driven in rotary motion and by the measurement of dynamic loads applied in the support lateral planes to be symmetrically relative to the rotor axis (e.g. U.S. Pat. No. 6,430,992, 73/66, 2002). A drawback with this method consists in complexity of processing of parameters to be measured for the determination of imbalance in each datum plane.
All the methods based on the impartment of rotary motion to the rotor when it is set up in the supports are limited with the used techniques affecting measurement results for vibrations caused by outrun of coupling bearing surfaces, journal ovalness, misalignment of outer rings, the presence of a lubricant in support bearings etc.
The present invention relates to a fundamentally different method of balancing that is characterized by a complex motion of a rotor. While using sufficiently simple techniques this method makes it possible to improve the accuracy of measuring imbalance parameters.
This method is known from the USSR Inventor's Certificate No. 297890, G01M1/38, 1971. According to this method the rotor is set up in the position, at which its axis is directed at an acute angle to the selected, e.g. vertical, axis, and oscillatory motion is imparted to the rotor relative to a fixed point of intersecting its axis with the selected vertical axis. In so doing, a rotor motion is provided such that a projection of a motion path of any rotor axis point onto a horizontal plane is symmetrical with respect to the vertical axis.
Improvement of this method, known from the Russian Patent No. 2105962, G01M1/38, 1993, is aimed at improving a balancing accuracy at the expense of decreasing the rotor angular oscillations affecting parameters to be measured. This method, like the above one, consists in imparting oscillatory motion to the rotor relative to a fixed point located on the rotor axis and measuring the rotor angular oscillation amplitude and phase, by which rotor imbalance parameters can be judged in one of the imbalance planes. To improve balancing accuracy, a reference system of measurements that makes it possible to decrease influence on the measured parameters of the rotor angular oscillations relative to its axis is configured. The reference system is configured by means of using a balanced body that is coaxial with the rotor; said body being set in motion simultaneously with the rotor. This method may be considered as the closest prior art with respect to the present invention.
In the implementation of this method, however, some rotor oscillations take place and, hence, balancing of the body in the plane perpendicular to the rotor axis is changed; as a result, balancing accuracy is affected negatively.
The closest prior art device to be used for the claimed method is a device known from the Russian Patent No. 2105962, G01M1/38, 1993 and designed for using the balancing method based on imparting the oscillatory motion to the rotor. This device comprises a bed plate, a shaft with a spherical support fit at its one end and joined to a drive shaft with a variable eccentric and being set up on the rotor and installed inside the balanced body on the elastically flexible flat part that makes it possible to offset relative to the balanced body axis, as well as unbalance control sensors, a reference signal sensor and a sensor output signal processing unit. The signal processing unit comprises a pulse sequence generator with its input connected to the reference signal sensor, a binary counter, a trigger, a storage register block, a decoder and an imbalance angular coordinate and value indicator. The above unit elements are interconnected in accordance with the circuit providing measurement of imbalance parameters.
The drawback to this device, as well as the known method consists in not sufficiently high rate of balancing accuracy because of rotor oscillations in the plane that is perpendicular to its axis.